1. Field of the Invention
This invention relates to a communication cable and more specifically to a communication cable which is constructed to include both electrical wires and optical fibers.
2. Description of the Related Art
In the operation of machines that are computer controlled, there is required a communication cable. The communication cable would extend between the machine and the computer. Typical machines or pieces of equipment would be metal forming machines or any machine whose operation is controlled by computer.
It is common that the computer is spaced some distance from the machine. To connect the machine to the computer a cable is required. Normally, in a place of business, there will be several machines. Each of these machines produce electromagnetic interference (EMI) or radio frequency interference (RFI). There also can be produced ground loops and ground currents. The typical cable that interconnects the machine to the computer basically contains just electrical wires. The transmission of the electrical signals over these electrical wires can be interfered with by the EMI, RFI, ground loops and or ground currents. This interference can result in incorrect control signals being supplied from the machine to the computer or vice versa. In the past, this problem, though relatively common, has been just lived with as there has not been any known structure that has been available to correct the problem. Extensive shielding, extra heavy ground wires and in general keeping cables short allowed the systems to work. In some cases marginally.
One way in which to avoid this kind of interference with electrical wires is to eliminate the electrical wires so that the control signals are not transmitted along electrical wires. One way this could be done is by using of fiberoptics. However, in the past, fiberoptic cables were relatively mechanically sensitive and frequently installations could be somewhat abusive. The result was the fiberoptic cable broke or deteriorated to where it was inoperative. The fiberoptics only needs to be used in conjunction with the control signals. The power that is transmitted between the computer and the machine can be transmitted by electrically conducting metallic wires as the power transmitting wires are sensitive to the EMI and RFI.
There is a need to construct a cable which includes not only electrical wires for transmitting of power but also fiberoptics for transmitting of control signals. The cable must be constructed to withstand abuse, and because it looks and functions just like a regular electrical cable, the user can be completely unknowledgable of the fact that it is a fiberoptic cable. The use of such a cable would be extremely critical and desirable in sensitive applications thereby completely avoiding any kind of electronic or electrical interference to the control signal.